The invention relates to improvements in machines for brewing hot beverages, and more particularly to improvements in coffee making, tea making or like machines wherein electrical, electronic and other components are installed in the interior of a hollow base forming part of or constituting the housing of the machine.
An automatic coffee maker of the type to which the present invention pertains comprises a container for fresh water on top of the base, a warming plate in the base, an electric heater in the base beneath the warming plate, a filter holder which can receive filter paper with a metered quantity of flavoring agent (such as ground coffee beans), and conduits for conveying water from the container to the heater and from the heater to the filter holder. The latter is or can be supported by a vessel, such as a coffee pot, which gathers freshly brewed coffee and rests on the warming plate. It is also known to install the warming plate in a ring-shaped insulator which confines an annular seal of the warming plate and surrounds a bridge serving to bias the electric heater against the underside of the warming plate so that the heater can heat water and can also maintain the warming plate at a desired temperature. Reference may be had, for example, to published German patent application No. 25 45 548 which discloses a sheet metal warming plate and an electric heater (a so-called through flow heater) adjacent the underside of the warming plate. The heater is engaged by three yokes having end portions cooperating with internal projections of the hollow base of the housing to urge the heater against the warming plate. The internal projections of the base are adjacent an opening for the warming plate, and each such projection has a tapped blind bore for a portion of a screw. The shanks of the screws also extend through the respective yokes and can carry distancing elements. A drawback of the just described machine is that the assembly of its parts is a time-consuming operation because the screws can be applied only after the warming plate, the electric heater and the yokes are already inserted into the base of the housing. Moreover, at least one of the several screws is likely to become loose when the machine is in use to thus affect the exchange of heat between the electric heater and the warming plate.
Published German patent application No. 34 15 167 discloses a machine wherein the underside of the warming plate carries a screw or bolt which cooperates with a nut to maintain the heater in contact with the warming plate. A drawback of this machine is that the extent of heat exchange between the warming plate and the electric heater depends upon the axial position of the nut relative to the screw or bolt. Such position can be altered if the machine is subjected to vibratory or other stresses which are likely to loosen the nut.
It is further known to employ a yoke which can be attached to a screw at the underside of the warming plate and is used to maintain the electric heater in contact with the warming plate. The shank of the screw extends through a hole provided in the yoke and bounded by a smooth surface. The screw cooperates with a nut to urge the yoke against the electric heater and to thus maintain the heater in contact with the warming plate. The free ends of the yoke engage an insulator which is installed in the base of the housing. This machine exhibits the drawbacks of the aforediscussed machines, i.e., it is necessary to rely on externally and internally threaded connecting elements and such elements are likely to become loose in response to vibration and/or other stray movements of the machine.